Amid the increasing challenges posed by climate change, scientists are conducting intensive research to identify the thermal conditions that humans can adapt to in a world experiencing rising temperatures, without relying on air conditioning systems. The United States recently witnessed unprecedented heatwaves, occurring just weeks into summer, which led to at least 38 deaths due to heat-related complications this season. Researchers are exploring the new limits of human tolerance in the face of extreme heat waves, focusing on determining temperatures that individuals can endure without air conditioning, as well as identifying when certain areas may reach deadly thermal levels.
Some scientists express concern that a severe heatwave may hit an area lacking reliable air conditioning systems, potentially resulting in a human catastrophe. Recent studies indicate that heat tolerance thresholds may be much lower than previously believed, especially for vulnerable groups such as the elderly and people living in dry climates. Jennifer Vanos, an associate professor in the School of Sustainability at Arizona State University, in her research published in Nature Communications last November, states that the physiological thresholds for heatstroke are much lower than previously known, particularly in dry heat. Human sweating ability is limited, particularly for older adults. She emphasizes that, in the United States, heat-related deaths should be 100% preventable through the provision of air conditioning in necessary locations, which is not available in some parts of the world.
Scientists highlight the following elements regarding how to cope with high heat and humidity:
- **Body Cooling:** The human body cannot withstand temperatures reaching 43 degrees Celsius (about 109.4 degrees Fahrenheit).
- **Importance of Humidity:** Humans rely on sweating to cool their bodies; however, in humid environments, sweat may not evaporate efficiently, leading to heat accumulation inside the body and increasing the risk of heatstroke.
- **Wet Bulb Temperature:** Scientists use this measurement to assess the combined effects of heat and humidity, considering 35 degrees Celsius (about 95 degrees Fahrenheit) at 100% humidity as the maximum threshold for human tolerance without cooling.
- **Reassessing Heat Tolerance Limits:** Recent studies suggest that previous thresholds might be exaggerated, and the actual wet bulb temperatures that can be tolerated may be lower, particularly for younger and healthier individuals.
- **Increased Risks for the Elderly:** Older adults face heightened risks, especially in dry environments, where the physiological thresholds for heatstroke may be much lower than previously thought. Vanos warns that believing in a single survival threshold can be dangerous, as tolerance varies from person to person based on multiple factors such as age and overall health.
